Even if the CCC does not contain specific definitions like "airsoft," "uncontrolled firearms," etc, airsoft guns are still not strictly considered firearms.
Section 84(3) Part D of the CCC explicitly states what isn't a firearm.
(3) For the purposes of sections 91 to 95, 99 to 101, 103 to 107 and 117.03 of this Act and the provisions of the Firearms Act, the following weapons are deemed not to be firearms:
(d) any other barrelled weapon, where it is proved that the weapon is not designed or adapted to discharge
(i) a shot, bullet or other projectile at a muzzle velocity exceeding 152.4 m per second or at a muzzle energy exceeding 5.7 Joules, or
(ii) a shot, bullet or other projectile that is designed or adapted to attain a velocity exceeding 152.4 m per second or an energy exceeding 5.7 Joules.
Airsoft guns fire no where near 5.7 Joules. Most come in at under 1.4J or so (if that).
There may be a court ruling that states that anything over 214 FPS is a firearm, but the CCC explicitly states that this isn't true. Should there ever be a case where this comes up, we'll see where the government lands on the issue. However, will the law really change based on precedent from one single case? Precedent that would almost certainly be challenged if it came to it?